While you're not completely wrong, your estimation on replaceability of engineers in general isn't just "hey monster.com please send 5x general engineers my way" after you lose a few. Especially when it comes to senior positions, or unique aerospace roles like at SpaceX. There's a reason those salaries go sky high at times.

That aside, in many cases it takes an engineering-minded businessman to create the greatest enterprises. Not just in valuation, but in general value and appreciation in fields where one can do a lot of good but not get a lot of profit.